Preparation of dual-targeted pH-sensitive DOX prodrug-microbubble complex and drug release experiment in vitro

Abstract

Objective To prepare dual-targeted pH-sensitive DOX prodrug-microbubble complex and explore the characterization of complex with ultrasound as well as drug release in vitro. Methods Dual-targeted ligands, cRGD and folate were conjugated with heparin using carbodiimide method, and then the dual-targeted pH-sensitive DOX prodrug was synthesized by coupling DOX via a pH-sensitive hydrazone bond. The prodrug was combined with microbubbles to prepare complex by biotin-avidin system. The characterization of complex with/without ultrasound was investigated for size, morphology and drug loaded capacity.In vitro drug release manner of complex with/without at different pH was analyzed. Results DOX content of the prodrug determined by UV Spectrophotometry was about 18.9%. Dynamic laser light scattering analysis(DLS), corresponding to transmission electron microscope(TEM) findings, revealed its inhomogeneous size distribution [mean size (159.7±24.5)nm and (1 089.0±174.9)nm]. However, the complex was dispersed into uniform fragment after ultrasound irradiation[mean size (155.9±29.8)nm, polymer dispersity index(PDI) 0.22, Zeta potential -(20.6±3.4)mV]. The cumulative release rate of DOX from both complex and complex with ultrasound at pH 5.0 were much faster than that at pH 7.4, displaying a pH-triggered release manner. Conclusions Dual-targeted pH-sensitive DOX prodrug-microbubble complex displays excellent drug release activity in acid environment. Uniform fragment and smaller particle size of complex could be achieved via ultrasound irradiation, promoting DOX accumulation within tumor tissue and facilitating in vivo antitumor ability. Key words: Sonication; Doxorubicin; Microbubbles; Targeted therapy